Articles such as hard disks, semiconductor wafers, delicate optics, etc., often must be precisely cleaned in order to remove contaminants, either during or after a process for manufacturing the articles. For example, resist strip and residue clean typically are needed between etch, implant and deposition steps in IC fabrication processes. Conventional dry-type strip/clean sequences typically use plasma to ash resist and wet chemicals to clean residues. Resist stripping is typically carried out using dry plasma ashing. Conventional O2 plasma ashing at high temperature tends to leave polymeric residues that require acids and/or organic solvents for removal. Wet chemistries generally are not desirable due to non-uniformities, selectivity to exposed layers and incomplete resist removal because of mass transport and surface tension associated with the solutions. In particular, for a post metal etch, wet processes cause corrosion that is detrimental to the final products (computer chips, hard disk, etc). A variety of alternative cleaning methods have been employed with varying degrees of success. Certain of such methods that have been attempted involve imparting carbon dioxide snow onto the article to be cleaned. An example of a conventional carbon dioxide cleaning system is described in U.S. Pat. No. 5,766,061.
In semiconductor fabrication, photoresist removal generally is the most repeated step. In metal etch processes photoresist typically is removed in situ before exposing the wafer to atmosphere. This helps to prevent metal line corrosion due to etch byproduct deposition on the top and sidewalls of the metal lines. Photoresist removal usually includes two steps: a bulk photoresist removal and post etch residue removal. These byproducts, often referred to as polymers, generally contain Ti, TiN, Al, Cl Si, O, C and their compounds. Post etch residue removal techniques typically include using solvent or plasma treatment followed by DI rinse and then wafer drying. Using multiple tools for post etch residue-cleaning increases the cost and reduces the throughput in the overall manufacturing operation.
It would be desirable to have an all dry cleaning method that does not use wet chemistry and completely removes post etch polymer residue with high throughput while minimizing or reducing the possibility for metal corrosion.